Core taker devices



Nov. 30, 1965 H. o. MOHR 3,220,491

CORE TAKER DEVICES Filed Dec. 17, 1963 ,34 flax vey 0. Mofir 36INVENTOR.

WM /Jdzu 49 ATTORNEY free Patented Nov. 3%, 1965 3,220,491 QGRE TAKERDEVICES Harvey 0. Mohr, Houston, Tex assignor to Sehiumherger WeltSurveying Corporation, Houston, Tex a corporation of Texas Filed Dec.17, W63, Ser. No. 331,234 Claims. (Cl. 175-4) This invention relates toapparatus for obtaining solid samples of earth formations and, moreparticularly, pertains to a new and improved core-taking apparatus forobtaining a solid sample of earth formation material.

Generally, cores or samples of earth formation material are obtained bylowering a side wall sample taker assembly into the borehole to thelevel of the formation to be investigated. The sample taker assemblyineludes a gun body which receives a number of hollow core-takingbullets together with explosive means which are selectively operable sothat the bullets may be im pelled towards and into a formation, with thehollow interior of the bullets thereby receiving the formation material.Usually, the core bullet is secured to the gun body by one or moreflexible retrieving connections so that a pull, as by raising the gunbody, serves to withdraw the core bullet with a formation sample fromthe earth formations. Thus, a formation core sample can be retrieved tothe surface of the earth for examination and testing.

However, many problems are presented by the variety of formations whichare encountered in sampling operations. For example, the types offormations may be generally classified as (1) soft, (2) medium, (3)firm, (4) hard, and (5) extra hard. Thus, the problems may vary from thedifficulty in geting the bullet into the extra hard formations withoutdamage to the difficulty encountered in soft formations in thewithdrawal of the core bullet from the formation. To obtain core samplesfrom the various types of formations, different types of core bulletshave been designed to meet the various conditions arising. Aside fromthe problem of retrieving the core bullets, it is, of course, necessaryto obtain a core-sample with is representative of the formation tested.

Particularly in the soft to firm formations, recovery of core bulletshas been facilitated by providing the core bullet with a separableforward portion in the form of an annular cutting ring which generallyhas a slightly greater outer diameter than the core barrel. Thus, thering forms an enlarged hole relative to the body of the bullet toalleviate sticking of the bullet body in the formation. When a poll isexerted on the body of the bullet, it should separate from the cuttingring thereby to leave the cutting ring in the formation. Various cuttingring attachments have heretofore been used such as the types disclosedin Patents No. 2,923,530, No. 3,101,- 797 or No. 3,072,202.

It has been found in many instances that the core bullet becomes sofirmly embedded that in pulling on the bullet in the formations, thewire-retrieving connections are broken.

Accordingly, it is an object of the present invention to provide new andimproved core-taking apparatus for minimizing the retrieval pullrequired on a core-taking bullet.

Another object of the present invention is to provide new and improvedcore-taking apparatus which is selfretracting from earth formations.

Still another object of the present invention is to provide new andimproved core-taking apparatus which is explosively self-retracting fromearth formations.

In apparatus for obtaining a core sample, in accordance with the presentinvention, a gun body receives one or more core-sampling bullets whichmay be disposed lengthwise of the gun body. The bullet is adapted to beimpelled toward and into earth formations by explosive means and has abody member with a cutting ring member releasably received on itsforward end. Means are provided to operate after the bullet has left agun body and is in the earth formations to move the body memberrearwardly relative to the ring member. Thus, the body member isretractable from earth formations relative to the ring memberindependent of the usual retrieving wire members.

The novel features of the present invention are set forth withparticularity in the appended claims. The present invention, both as toits organization and manner of operation together with further objectsand advantages thereof, may best be understood by way of illustrationand example of certain embodiments when taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a view in partial cross-section of apparatus embodying thepresent invention for obtaining a core sample and illustrated in a wellbore;

FIG. 2 is a view in cross-section of a bullet embodying the presentinvention;

FIG. 3 is a view in cross-section of a bullet embodying another form ofthe present invention;

FIG. 4 is a view in cross-section of a bullet embodying another form ofthe present invention.

In FIG. 1 of the drawings, there is shown a gun block or body It!disposed in a borehole l1 opposite a formation 12 of interest. Usually,borehole 11 contains a drilling mud 13.

Gun block it has a cylindrical bore 14 adjoining a bore 15 of smallerdiameter, the bore 15 forming a powder chamber which terminates short ofthe rear surface 16 of the gun block. Chamber 15 contains an appropriateand conventional explosive propellant 17 while bore 14 receives agenerally cylindical core-taking device or bullet assembly 18constructed in accordance with the present invention. Although notillustrated, gun block 10 generally contains additional bulletassemblies in respective bores distributed along a vertical axis for thegun block.

Bullet assembly or bullet 18, near its rearward end, has an annulargroove which receives an O-ring 19 to provide a fluid-tight seal for thebullet assembly 18 in the bore 14, and flexible retrieving wires 20 aresecured in a conventional manner between the bullet assembly and gunblock it to permit the bullet body of the assembly to be retrieved. Aconventional igniter 21 suitably mounted in the block 10 may be employedto detonate the explosive propellant 17 and thereby propel the bullet istoward and into the formation.

Referring now to FIG. 2, bullet or bullet body member 18 is comprised ofthree parts, to wit, a forward tubular sample-receiving core part 21, anintermediate coupling part 22 and a rearward bottom part 23. Forwardpart 21 has a forwardly facing shoulder 24 which releasably receives acutting ring or release member 25 and a snap ring 26 is provided toinsure retention of ring 25 on the shoulder 24 of part 21. Ring member25 has the usual, conically shaped forward surface and disposed slightlyrearwardly of the forward cutting edge 27 on the tubular part 21. Ringmember 25 is also slightly greater in over-all diameter than thediameter of the body portion rearwardly of the cutting ring member toreduce the area of the bullet in the formation subject to hydrostaticpressure. The purpose of the cutting ring member 25 is to provide anoversized hole so that the outer body of the bullet 18 is prevented frominitimate contact with the earth formations, the ring member 25 beingleft embedded in the earth formations. Of course,

azasr I the precise connection and arrangement of the ring memberrelative to the bullet body is immaterial to the present invention solong as the ring member when in the earth formations is releasable fromthe bullet body. The above-described ring arrangement, however, ispreferable since the forwar dend of member 21 extends beyond ring 25 andobtains a better core sample more reliably.

Tubular core part 21 also has ports 28 in its side walls and connections29 for attachment of retrieving wire elements 20 to the bullet body.

Coupling part 22 of bullet 18 provides a bottom 30 for the tubular corepart 21 and has a rearward threaded bore 31 receiving a threaded tubularextension 32 of bottom part 23. Bottom 23 has a portion 33 forming apiston which is slidably and sealingly received in gun bore 14 by meansof the O-ring 19. An annualr recess 22a which faces forwardly from thebottom part is formed between portion 33 and extension 32. Slidably andsealingly received in recess 22a is a piston portion 34 ofself-releasing sleeve 35. Piston 34 has inner and outer groovesreceiving O-ri-ngs 36, 37 so that the sleeve 35 is sealed in the recesswhile a shoulder 38 on the sleeve abuts the upper end of bottom portion33. An O-ring 39 is provided on the intermediate part 22 to seal thispart relative to sleeve 35 and chamber 40 is formed between sleeve 35and parts 22, 23 and is pressure sealed by the O-rings 37, 39. Sleeve 35has a forward end suitably slotted to accommodate connections 29 and anend surface 41 which is adjacent to the cutting ring member 25.

Coupling part 22 has .a chamber 42 in which a centrally located,downwardly facing firing pin 43 is located. Spaced from the firing pin43 by a frangible tube 44 is a tubular hammer 45 carrying a percussionexplosive cap 46, the hammer normally being held above expolosivematerial 48 in the extension. Hammer also carries a power train 47. Thelowermost end of extension 32 i coupled by a passage 49 to the annularrecess 22a below piston 34.

In operation, when the powder 17 is ignited, the bullet is acceleratedfrom bore 14 toward and into adjacent earth formations. Snap ring 26 isdisplaced from its groove leaving the cutting ring 25 free, the cuttingring staying on the bullet body due to the forward movement of thebullet body. As the forward end of the bullet pentrates the formation,the cutting n'ng makes a large hole and keeps the portion of the bulletand sleeve 35 rearwardly of the ring from intimate contact with theformation.

As the bullet assembly impacts and lodges itself in the formation, ithas a very rapid deceleration. The firing hammer 45 which is looselyfitted inside the tubular extension 32 has the same velocity as thebullet assembly, but as the bullet assembly decelerates from formationimpact, the firing hammer 45, being a loosely fitted or a floatingmember, will fly forward and crush the crushable spacer 44. Theprimercap 46, which is held in the firing hammer 47, will then strike thefiring pin 43 which is held in coupling part 22. The primer cap 46 willthen ignite. This ignition sets ofi the powder 47 located inside thefiring hammer. The power 47 in the firing hammer will, in turn, set offthe powder 48 located inside the extension 32. The powder 47 can be usedalso as a timing device by varying the length or diameter of the columnof powder or by using powders of different burning speeds. Thesevariations could be easily made to be a time delay device before powder48 is ignited. The burning of the powder 48 creates a high pressure asit burns in the enclosed volume. This high pressure bleeds through thepassage 49 causing a pressure build-up behind piston 34. The size of thepassage 49 can also be used as a metering device. The pressure buildingup behind piston 34 will move sleeve 35 in such a manner with respect tothe bullet assembly so as to reduce the air chamber 40 bounded by seals39 land 37. As the chamber 40 is reduced, the sleeve 35 is forcedagainst the release ring 25. The force pushing on the release ring isequal to area bounded by the seals 36 and 37 times the pressure createdby the burning powder 48. There is an equal and opposite force acting onthe part 22 from the burning powder, and this force pulls the bulletfrom the formation and through the release ring 25. The pulling of thebullet from the formation breaks the seal of the differential pressurecaused by the mud. With the differential pressure seal broken, thebullet can easily be pulled from the formation by the retrieving wires.

The entire assembly, with core, but less snap ring 26 and release ring25, is returned to the surface via the wires 20 attached to the gunblock 1.

The apparatus of FIG. 3 is essentially the same as the apparatus of FIG.2 except that the explosive material 48 is coupled by an explosive delaytrain 47a in a passage to the main explosive 17 for the bullet.

Thus, at the same instant the powder 17 in gun block 1% is ignited, therelatively slow-burning powder 17 in part 22 is ignited. The burningspeed of powder 47 and the length and diameter of the column of powderare to insure that the bullet has struck the formation before the powder48 is ignited. Powder 48 is also a relatively slow-burning powder whichburns and creates a high pressure inside the chamber behind the piston34. The pressure build-up will move sleeve 35 in such a manner withrespect to the bullet assembly so as to reduce the air chamber 40 sothat sleeve 35 is forced against the release ring 25. The force pushingon the release ring is equal to the area bounded by the seals 36 and 37times the pressure created by the burning powder 48. There is an equaland opposite force acting on the bottom part 22 from the pressurecreated by the burning powder 48, and this force pulls the bullet fromthe formation and through the release ring 25. The pulling of the bulletfrom the formation breaks the seal of the differential pressure causedby the mud. With the differential pressure seal broken, the bullet caneasily be pulled from the formation.

The entire assembly, with core, but less snap ring 26 and release ring25, is returned to the surface via the fasteners 20 attached to gunblock 16.

Referring now to FIG. 4, another embodiment of the present invention isillustrated which is essentially the same as the embodiment of FIG. 2.In this embodiment, instead of explosive material, the tubular extension38 contains a glass assembly with chambers enclosing gas pressureforming chemicals 50, 51 disposed above an elastomer shock absorber 52.

As the bullet penetrates the formation, the release ring 25 makes alarge hole. As the bullet assembly impacts and lodges itself in theformation, it has a very rapid deceleration. The deceleration will causethe glass or fragile capsule assembly, being loosely fitted in thepiston 9, to fly forward, crushing the crushable spacer 44. Thebreakable capsule assembly will then strike pin 43 which will break thecapsule assembly. The capsule assembly containing two or more chemicals50 and 51 which, when the capsule assembly is broken, will react andform a gas when they come in contact with each other. The capsuleassembly is protected from breakage due to rapid acceleration, whenpowder 17 is ignited, by shock-absorbing material 52.

As the chemicals 5!), 51 come in contact due to the capsule assemblybeing broken, a high-pressure gas is formed in their place. Thehigh-pressure gas bleeds through the passage 49 and builds up a pressurebehind piston 34. The pressure build-up will move the sleeve 35 in sucha manner with respect to the bullet assembly so as to reduce the airchamber 40. As the air chamber 40 is reduced, the sleeve 35 is forcedagainst the release ring 25. The force pushing on the release ring isequal to area bounded by the seals 36 and 37 times the pressure createdby the reacting chemicals 50 and 51. There is an equal and oppositeforce acting on the part 22 from the reacting chemicals, and this forcepulls the bullet from the formation and through the release ring 25. Thepulling of the bullet from the formation breaks the seal of thedifferential pressure caused by the mud. With the differential pressureseal broken, the bullet can easily be pulled from the formation.

The entire assembly, with core, but less snap ring 26 and release ring25, is returned to the surface via the fasteners 20 attached to the gunblock 1.

While particular embodiments of the present invention have been shownand described, it is apparent that changes and modifications may be madewithout departing from this invention in its broader aspects and,therefore, the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

What is claimed is:

1. A formation core-taking device adapted to be fired from a gun bodyinto earth formations about a well bore comprising: a tubularcore-taking body member having a forward end, a formation-cutting ringmember releasably received on said forward end, means operativelycoupled between said body member and said ring member and responsive togas pressures developed after ejection from a gun body for providing aforce on said ring member, and means coupled to said pressure-responsivemeans for developing gas pressures in said body member upon impact ofsaid device with earth formations and providing a force between saidbody member and said pressure-responsive means to urge said body memberand ring member in opposite directions relative to one another when saidring member and forward end of said body member are embedded in earthformations.

2. A formation core-taking device including a portion adapted to bereceived in a gun body and fired therefrom into earth formations about awell bore comprising: a tubular core-taking body member having a forwardend, a formation-cutting ring member releasably received on said forwardend, a sleeve member with a piston portion, means forming a cylinder insaid body member for receiving said piston portion, said sleeve memberhaving a forward portion for engagement with said ring member, and meansin said body member for supplying gas pressure to said piston portionupon impact of said device with earth formations.

3. A formation core-taking device including a portion adapted to bereceived in a gun body and fired therefrom into earth formations about awell bore comprising: a tubular core-taking body member having a forwardend, a formation-cutting ring member releasably received on said forwardend, a sleeve member with a piston portion, means forming a cylinder insaid body member for receiving said piston portion, said sleeve memberhaving a forward portion for engagement with said ring member, and meansfor supplying gas pressure to said piston portion upon impact of saiddevice with earth formations including explosive means andimpact-responsive igniter means.

4. A formation core-taking device including a portion adapted to bereceived in a gun body and explosively fired therefrom into earthformations about a well bore comprising: a tubular core-taking bodymember having a forward end, a formation-cutting ring member releasablyreceived on said forward end, a sleeve member with a piston portion,means forming a cylinder in said body member for receiving said pistonportion, said sleeve member having a forward portion for engagement withsaid ring member, and means for supplying gas pressure to said pistonportion after said device is in earth formations including explosivemeans with a time-delay explosive train adapted to be disposed inigniting relationship to explosive for firing said device from a gunbody.

5. A formation core-taking device including a portion adapted to bereceived in a gun body and fired therefrom into earth formations about awell bore comprising: a tubular core-taking body member having a forwardend, a formation-cutting ring member releasably received on said forwardend, a sleeve member with a piston portion, means forming a cylinder insaid body member for receiving said piston portion, said sleeve memberhaving a forward portion for engagement with said ring member, and meansfor supplying gas pressure to said piston portion including chemicalgas-forming means and impact responsive means for activating saidgas-forming means upon impact of said device with earth formations.

References Cited by the Examiner UNITED STATES PATENTS 2,809,805 10/1957Laval 4 2,923,530 2/1960 Fields 175-4 XR 3,072,202 1/1963 Brieger 175-43,101,797 8/1963 Brieger 175-4 CHARLES E. OCONNELL, Primary Examiner.

2. A FORMATION CORE-TAKING DEVICE INCLUDING A PORTION ADAPTED TO BERECEIVED IN A GUN BODY AND FIRED THEREFROM INTO EARTH FORMATIONS ABOUT AWELL BORE COMPRISING: A TUBULAR CORE-TAKING BODY MEMBER HAVING A FORWARDEND, A FORMATION-CUTTING RING MEMBER RELEASABLY RECEIVED ON SAID FORWARDEND, A SLEEVE MEMBER WITH A PISTON PORTION, MEANS FORMING A CYLINDER INSAID BODY MEMBER FOR RECEIVING SAID PISTON PORTION, SAID SLEEVE MEMBERHAVING A FORWARD PORTION FOR ENGAGEMENT WITH SAID RING MEMBER, AND MEANSIN SAID BODY MEMBER FOR SUPPLYING GAS PRESSURE TO SAID PISTON PORTIONUPON IMPACT OF SAID DEVICE WITH EARTH FORMATION.